(1) Field of the Invention
This invention relates to deodorized polyolefins and a process for the preparation thereof, and more particularly relates to purified polyolefins prepared by deodorizing Ziegler process polyolefins having off-odor caused by a catalyst deactivating agent present in the Ziegler process polyolefins, and to a process for the preparation of the purified olefins.
(2) Description of the Prior Art
Recent proposals of the so-called high activity catalyst in the process for the preparation of polyolefins by use of Ziegler catalyst have resulted in remarkably simplifying the aforesaid process. Examples of omitted steps in the aforesaid simplified process compared with the classic preparation process include an amorphous polyolefin separation step, a solvent recovery step in the case of a gaseous phase process, a deashing step, and the like. However, even in the case where the deashing step can be omitted, crude polyolefins resulting immediately after polymerization must be subjected to a purifying step or a catalyst deactivating step prior to being passed, to the following step, because a catalyst residue contained in the crude polyolefins has some catalytic activity remaining therein. Examples of the deactivating agent, which reacts with the catalyst for the deactivation thereof, include water, alcohols, alkylene oxide, and the like. Of these deactivating agents, alkylene oxide is widely used as the deactivating agent due to easiness in handling and to high deactivation effect. However, polyolefins purified by use of alkylene oxide (hereinafter referred to as polyolefins purified with alkylene oxide) have such disadvantages that products molded from polyolefins purified with alkylene oxide such as molded parts, films, fibers and other workpieces have a peculiar off-odor, which reduces commercial values of the molded products as above and is liable to make the molded poriducts impossible to be used for some applications.
However, the fact that polyolefins purified with alkylene oxide have disadvantages as above is not publicly known prior to the filing of this patent application, but has newly been found as the result of studying dependence of effect on cause between the peculiar off-odor of molded products and the deactivating agent.
With an aim of neutralizing trace amounts of acid substances in the catalyst residue contained in the polyolefins not purified, for example, Japanese patent laid-open publication No. 3947/1974 discloses a process in which calcium hydroxide or magnesium hydroxide is mixed therewith, and Japanese patent laid-open publication Nos. 49285/1977 and 80447/1980 disclose a process in which hydrotalcite is mixed therewith. However, the aforesaid processes are unsatisfactory to solve the problems of deodorization described as above.